Water-soluble cationic vinyl polymers are widely used in industry as process aids for carrying out separation processes by means for example of flocculation, coagulation, retention and dehydration. Among other things, they come into use in water preparation and waste water cleaning, in the paper, coal and metal ore industries, in obtaining petroleum and in the foodstuffs industry. Used mostly in small quantities they have in part gained an importance in determining technology.
Manufacture of these polymers is effected by radical homo- or copolymerisation in the homogeneous or heterogeneous phase (C. L. McCormick, J. Bock and D. N. Schulz: Water-Soluble Polymers, in: Encyclopaedia of Polymer Science and Technology, Wiley, New York, 1989, Vo. 17, Page 730 and following). The homogeneous solution polymerisation in water has the disadvantage that even at polymer contents below 10% by mass, highly-viscous systems are present, which do not permit further increase in the content of active ingredient. The low polymer proportion in the final product leads to poor space/time yields in synthesis and to increased costs in transport to the user. Inverse immersion polymerisation in organic solvents as a carrier phase gives substantially higher contents of solid matter. This however has the disadvantage that using the solvents requires special protective measures, and in application of the products all of the solvents pass into the environment (J. Dautzenberg, W. Jaeger, J. Kotz, B. Phillipp, Ch. Seidel, D. Stscherbina: Polyelectrolytes, Carl Hanser Verlag, Munich 1994, Page 13 and following). Inverse suspension polymerisation in hydrophobic combustible solvents as a carrier phase finally leads, after isolation and drying of the polymers, to pulverulent products. The multi-stage process is however cost-intensive and requires much energy (H. Spoor, Angewandte Makromoleculare Chemie 123/124 (1984) Page 1 and following).
Therefore there was proposed as an alternative the manufacture of dispersions of water-soluble polymers without organic solvents as carrier phase. The document EP 183 466 describes the polymerisation of water-soluble monomers in aqueous solutions of inorganic salts in the presence of polyoles with molecular weights of up to 600 g/mol and/or polyelectrolytes obtained by homopolymerisation of ionic vinyl monomers or their static copolymerisation, as dispersion stabilisers. The Canadian Patent 2 096 472 (DEP 42 16 167.3 1992/05/18) describes the polymerisation of a combination of water-soluble and hydrophobic monomers, if necessary in combination with an amphiphatic monomer, in the presence of a polyalkylene ether or of a polyelectrolyte which is incompatible with the dispersed polymer and has molecular weights of &lt;5*10.sup.5 g/mol. The latter serves as a dispersion stabiliser. Preferably, poly(diallyldimethylammoniumchloride) is used. The resultant dispersion-forming polymer has molar masses of at least 10.sup.6 g/mol.
The disadvantage of the method according to EP 183 466 resides in the fact that the viscosity of the resulting dispersions is still comparatively high. A particular disadvantage however is that during the course of polymerisation viscosity maxima are exceeded, which correspond to the viscosity of solution polymerisations, and thus render the process technology difficult. The disadvantage of the Canadian Patent 2 096 472 is that considerable quantities of dispersion stabiliser, up to 80% by mass with respect to the monomer used, are brought into use. Here also the viscosity of the polymerising system can be greater than the viscosity of the end product. A disadvantage in both named methods is that the resultant dispersions coagulate after relatively short times and therefore the storage capacity is restricted.